One method of preserving seafood for a relatively short period is natural drying, which is called "Overnight Drying". Fresh fishes are cut open to remove inner organs, and what remaines is rinsed from the opened fishes. The opened fishes are put on bamboo lattices to be dried all day and all night long. The "Overnight Drying" will put opened fishes in a semi-dried condition, and the so semi-dried products can be preserved for a relatively short period.
Such a natural drying method can be used in weather-permitting districts in limited seasons, and it requires a relatively large outdoor space for opened fishes to be set in order a and a lot of manpower is needed in drying.
In addition, there is a sanitary problem of contamination with dust and bacilli floating in the air, and there is a fear of deteriorating the taste of dried products due to oxidization. Usually it takes the whole day (24 hours) to dry opened fishes, and the opened fishes must be brought in houses when the weather is threatening. Therefore, a natural drying is a time-consuming and laborious work.
Alternatively indoor drying can be effected in sanitary rooms by using infrared lamps in place of sunlight. Such infrared heating will dry the surface of opened fishes and other foods in to a crisp condition, thereby confining free water inside to allow bacilli to breed. Otherwise, the oxygen gas remaining in the tissue of the food causes the surface of dried foods to detiorate due to oxidation.
Another drying method uses cold wind. Advantageously it takes 3 to 4 hours to dry foods in such a semi-dried condition as attained by the "Overnight Drying". The so dried products, however, are abundant in bacilli, and cannot be preserved for a long period without recourse to freezing preservation.